Among the many stark questions at the heart of the Trayvon Martin case is one simple query with huge implications: Does Florida's "Stand Your Ground" law encourage guys like George Zimmerman to take justice into their own hands? Or, as Florida Republicans argue, does it deter crime by ensuring anyone can kill in self-defense?

In fact, Florida's law -- which 22 other states have copied -- increases the homicide rate and fails to deter violent crime. That's the conclusion of a new study, at least.

The report comes from Texas A&M University, where economics professor Mark Hoekstra and research assistant Cheng Cheng looked at state level crime data from 2000 to 2009 in Florida and the 22 other states that have passed their own versions of Stand Your Ground.

Their results were conclusive, the pair says.

"The prospect of facing additional self-defense does not deter crime," they write. "We find no evidence of deterrence effects on burglary, robbery, or aggravated assault ... In contrast, we find significant evidence that the laws increase homicides."

The murder increase in states with Stand Your Ground isn't subtle, either. The pair found that after passing the law, states saw a 7 to 9 percent jump in murders and non-negligent manslaughters.

Surprisingly, they also found that the jump doesn't come from the increase in people claiming justifiable homicides under the new laws. Their research found only 50 such cases across the whole country per year since the laws have been passed; that number doesn't come close to explaining the jump in murders -- an additional 500 to 700 per year -- in Stand Your Ground states.